Re: 102 print developer storage as working solution
"Nicholas O. Lindan" <see@sig,com > wrote in message
news:13fn8aghrj44f57@corp.supernews,com ...
> "Lloyd Erlick" <Lloyd at @the-wire. dot com> wrote
>
>> Edwal 102 (Potassium version).
>
> Something like:
> H20 1l
> P.Sulfite 100g
> TSP 125
> Glycin 25
> P. Bromide 3
> (?)
>
>> I'm a little surprised to find a
>> developer that keeps a week in the form of a
>> partially used working solution.
>
> I believe it is Metol that's responsible for
> short tray life.
>
> Metol-less HQ, Glycin and Phenidone developers
> seem to last longer.
>
> Phenidone is often kept dissolved in 90+% isoproponol.
> I don't know if this is works with Glycin, I seem
> to remember Patrick Gainer mentioning Propylene Glycol
> as a keeping solvent.
>
> It is possible that a 1:4 liquid concentrate of
> Glycin and S. Sulfite would keep a long time.
>
> My guess is the actual ingredients of a bottle
> of Glycin are somewhat variable - in my experience
> it sometimes goes quickly, sometimes it lasts
> for a year.
>
>> Oh, I just thought of a question for the old
>> time experienced crew: would the ancient
>> practice of 'sweetening' or 'seasoning' a
>> freshly mixed batch of this developer with
>> ten or twenty per cent by volume of week-old
>> working solution be of any value? I've tried
>> this on several occasions with other
>> developers, and I have to admit I've never
>> seen the benefit.
>
> TTBOMK this is a practice used for motion picture
> developing where they want to keep the activity
> of the developer constant from the last film
> through a tank of old developer to the first
> film through a tank of fresh developer. Richard
> Knoppow would know: "Knoppow Knows" - does that
> count as nominative determinism?
>
> --
> Nicholas O. Lindan, Cleveland, Ohio
> Darkroom Automation: F-Stop Timers, Enlarging Meters
> http :// www .darkroomautomation,com /index.htm
> n o lindan at ix dot netcom dot com
>
Evidently some chemicals keep better in solution than in
powder form. Ammonium thiosulfate, the basic ingredient of
"rapid" fixers is one. This is why rapid fixer is sold as a
liquid concentrate rather than a powder. I don't know if
this is true of Glycin. I think the main reason for the long
life of your working solution is that it was well protected
from air in storage. Kodak gives lifetimes for some
developers when used in tanks with lids as a week, the bag
should be better depending on what plastic its made of.
Adding some used developer to fresh can keep its
performance more uniform. As developer is used it
accumulates reaction products. Some of these, like Bromide
and Iodide, come from the film or paper, some are from the
developing agents. The reaction products are not consistent
in their effects, for instance, the reaction products of
Metol are restrainers but those of Hydroquinone are
accelerators. In general the presence of sulfite tends to
reduce the effects of these reaction products. Also, in
developers containing both Metol and Hydroquinone the two
tend to regenerate each other also reducing the effects of
the reaction products.
Although fresh developer can have Bromide added to it to
act as an anti-fog restrainer the effect may not be quite
the same as developer which has additional reaction products
in it. The practice of adding some old developer to fresh
developer is a way of trying to keep the developer more
uniform in action.
Motion picture practice changed over the years. In the
early days most negative processing, and probably most print
processing, was carried out in rack-and-tank units mostly by
hand. As the volume of work became greater some processing
began to be done in machines. After the introduction of
photographic sound recording the requirements for processing
control became very much greater than is needed for the
picture alone so the use of automatic machine processing
rapidly became standard practice. Also at about the same
time (late 1920's) research was begun on replenishing. By
about the early 1930's systems of replenisment were devised
to extend the life of the developer and insure uniformity in
machines. The research continued because early replenishment
systems were not entirely satisfactory. I don't have numbers
for the life of processing solutions in current machines but
its very long. The developer and other solutions in current
automatic processing machines is not only replenished by the
addition of more developer but regerated by removing
dissolved silver and some other chemicals.
For the most part replenishment of B&W developers for
home use is not too practical because the volume of use is
too little. However, simple replenishment according to
instructions can keep many developers going for very long
periods of time (over a year). Ideally, the developer
performance should be tested by sensitometric means but this
is really necessary only when very critical work is being
done.
--
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix,net com,com